Title

Author

Document Type

Award Date

2002

Degree Name

Master of Science (MS)

Department

Wildlife and Fisheries Science

First Advisor

Steven R. Chipps

Keywords

nutritent, ecology, water quaility, south dakota, wyoming, pollution

Abstract

Productivity of Black Hills reservoirs varies considerably with summer water clarity (Secchi depth) ranging from 2.5 m in Stockade Reservoir to 9 m in Pactola Rservoir. Factors such as basin morphology, hypolimnetic oxygen concentration, nutrient inputs, and water residence time likely have an important influence on productivity in Black Hills reservoirs. In the upper Rapid Creek drainage, natural iron deposits may result in increased iron availability in downstream reservoirs, particularly Pactola Reservoir. In aquatic system, iron is an important agent that binds phosphorus under aerobic conditions. As a result, iron availability can have important implications for reservoir productivity and eutrophication. In this study, I quantified iron availability and limnological characters of four Black Hills reservoirs: Pactola, Deerfield, Sheridan, and Stockade. I also examined four streams with varying iron concentrations to quantify differences in periphyton biomass. Invertebrate abundance, and fish composition and abundance. Areal phosphorus inputs ranged from 0.53 mg P/m2/d in Deerfield to 7.3 mg P/m2/d in Stockade Reservoir while sediment phosphorus ranged from 0.7 mg P/g in Deerfield Reservoir to 1.8 mg P/g in Stockade Reservoir. Sediment iron was highest in Pactola (51.5 mg/g) and lowest in Deerfield (19.7 mg/g). Reservoirs that exhibited anoxia in their hypolimnia had significant increases (230%) in water column phosphorus near the sediment-water interface. However, reservoirs that remained well-oxygenated throughout the summer had low hypolmnetic phosphorus concentrations, implying increased buffering capacity to sediment phosphorus release. Interestingly, mean annual phosphorus concentration in Black Hills reservoirs was positively correlated to mean annual sediment P:Fe ratio. High iron content in Black Hills streams was associated with 1) reduced perphyton biomass, 2) low invertebrate abundance, and 3) reduced fish biomass. Periphyton biomass was lowest in North Fork Castle Creek (4.65 mg/m2) and highest in North Fork Rapid (21.70 mg/m2). Similarly, invertebrate abundance ranged from 489/m2 in North Fork Castle to 8700/m2 in North Fork Rapid. Fish abundance ranged from 44/100 m in North Fork Castle Creek to 141/100 m in Castle Creek. Fish CPUE was positively associated with invertebrate abundance, indicating that fish abundance may be related to available food resources. However, fish abundance in streams with high iron content was dominated by native species suggesting local tolerance to iron conditions may be important for reducing interactions with salmonids.